Macroscopic Interference Effects Research Articles

Spectrally resolved spatiotemporal features of quantum paths in high-order-harmonic generation

We experimentally disentangle the contributions of different quantum paths in high-order harmonic generation (HHG) from the spectrally and spatially resolved harmonic spectra. By adjusting the laser intensity and focusing position, we simultaneously observe the spectrum splitting, frequency shift and intensity-dependent modulation of harmonic yields both for the short and long paths. Based on the simulations, we discriminate the physical mechanisms of the intensity-dependent modulation of HHG due to the quantum path interference and macroscopic interference effects. Moreover, it is shown that the atomic dipole phases of different quantum paths are encoded in the frequency shift. In turn, it enables us to retrieve the atomic dipole phases and the temporal chirps of different quantum paths from the measured harmonic spectra. This result gives an informative mapping of spatiotemporal and spectral features of quantum paths in HHG.

Macroscopic Interference Effects in Resonant Cavities

We investigate the possibility of interference effects induced by a macroscopic quantum-mechanical superposition of almost orthogonal coherent states – a Schrödinger cat state – in a resonant micro-cavity. Despite the fact that a single atom, used as a probe of the cat state, on the average only change the mean number of photons by at most one unit, we show that this single atom can change the system drastically. Interference between the initial and almost orthogonal macroscopic quantum states of the radiation field can now take place. Dissipation under current experimental conditions is taken into account and it is found that this does not necessarily change the interference effects dramatically.

NEW MACROSCOPIC QUANTUM STATE IN PEROVSKITE-CRYSTALLINE CONDUCTOR WITH LOCALIZED CARRIER SYSTEM

The large zero-point oscillation of energy ~0.1–1 eV of strong coupling hole carriers in layered perovskite (LP) conductor is shown to provide effective field B* ~ 103–4 T causing fractional quantum Hall effect (FQHE) when space charge and moderate localization are present. The quasiparticle excitation spectrum of the FQHE system is calculated. The FQHE state is a macroscopic quantum state where macroscopic interference effect is expected. Using (001) La 2-x Sr x CuO 4-y (LSCO) film, we observed "dc dielectric interference" and the interference effect at 28 THz, which are explicable by the FQHE in the layered perovskite film.

Nodal phase correlation and macroscopic quantum effects in superconducting rings

We introduce the new concept of "nodal phase correlation" (NPC) into many-particle quantum mechanics. NPC is a particular quantum correlation among particles, which is important for current-carrying states of isolated systems. Mathematically it is characterized by a definite relation in configuration space between the phase and the modulus of the many-particle wave function. We illustrate the significance of NPC by showing the crucial role it plays in magnetic flux quantization and in certain macroscopic interference effects in superconducting rings. To this end we partly rederive the theory of these phenomena. Our method is based on the BCS theory. We critically examine previous work, in particular the single-particle pairing theory, which is considered to be a standard approach to magnetic flux quantization. This theory does not give rise to NPC. We are able to show that the corresponding many-particle wave function is in fact unrealistic and not consistent with the BCS theory of superconductivity.